The naturally occurring deazaadenosine antibiotics tubercidin, toyocamycin, and sangivamycin have demonstrated antitumor activity. In view of the considerable potential of this series of compounds, and compounds derived therefrom, a systematic study has been undertaken (1) to pinpoint the centers within these molecules which are crucial for favorable bio-activity and (2) to avail a large number of compounds of potentially more favorable cancer chemotherapeutic value. To this end the preparation of deaza analogs and related derivatives of the aforementioned antibiotics is being pursued.